CN113292525A - Preparation method of delta caprolactone - Google Patents
Preparation method of delta caprolactone Download PDFInfo
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Abstract
The invention relates to a preparation method of delta caprolactone, which comprises the following steps: dissolving a beta-dicarbonyl compound and a basic catalyst in a solvent for preheating; dripping acrylic acid alkyl ester into the reaction system to carry out Michael addition reaction; cooling the system, adding alkali, and then heating the reaction system to carry out saponification reaction; adding water, cooling the system, and adding a reducing agent for reaction; cooling the system, adjusting the pH value with acid, and performing post-treatment to obtain the delta caprolactone. The method has the advantages of simple process operation, high safety, high utilization rate of raw materials, short total time consumption and no generation of carbon dioxide.
Description
Technical Field
The invention belongs to the field of organic chemical synthesis, and particularly relates to a preparation method of delta caprolactone.
Background
Delta-caprolactone, also known as delta-caprolactone, has the molecular formula C6H10O2It is mainly used as edible essence and tobacco essence. The usual preparation comprises reduction of gamma-acetylbutyric acid with sodium amalgam followed by acidification, or boiling of delta-bromohexanoic acid with water or from 2-methylcycloPentanone is prepared by Bayer-Villiger reaction. However, sodium amalgam releases extremely combustible gas when meeting water, absorbs toxicity, belongs to a dangerous product with cumulative effect, namely, the raw material of the delta-bromohexanoic acid is very expensive and is more expensive than the product, and is not suitable for industrial production. In addition, the existing synthesis process involves multi-step reaction, so that the side reactions are more, the impurities are more, and the yield of the delta caprolactone is to be further improved.
The prior patent document 1 improves the method for synthesizing delta-caprolactone perfume, and the delta-caprolactone perfume is obtained by taking methyl acetoacetate and methyl acrylate as raw materials through Michael addition, decarboxylation and high-pressure reduction reaction. However, the process needs to use a large excess of methyl acetoacetate to control the Michael addition, which causes great material waste, the total yield of the process is about 67.7%, a sudden temperature rise phenomenon is easy to occur in the first Michael reaction process, the actual industrial production has certain dangerousness, and the overall reaction takes long time, which is more than 16 hours on average. In addition, carbon dioxide is generated while acetobutyrate is generated, the global warming problem is severe and environmental protection pressure is high nowadays, expensive equipment is required for carbon dioxide recovery, and the early cost of Carbon Capture and Sequestration (CCS) is high. Finally, the hydrogenation reaction needs to use a precious ruthenium carbon catalyst or a palladium carbon catalyst, and needs high-temperature and high-pressure hydrogenation, so that certain potential safety hazards exist.
List of references:
patent document 1: CN112321552A
Disclosure of Invention
Problems to be solved by the invention
In order to solve the problems in the prior art, the invention aims to provide a preparation method of delta caprolactone, which has the advantages of simple process operation, high safety, high raw material utilization rate, short total time consumption and no carbon dioxide generation.
Means for solving the problems
The invention provides the following technical scheme:
[1] a method for preparing delta caprolactone, wherein the method comprises the following steps:
1) dissolving a beta-dicarbonyl compound and a basic catalyst in a solvent for preheating;
2) dripping acrylic acid alkyl ester into the reaction system to carry out Michael addition reaction;
3) cooling the system, adding alkali, and then heating the reaction system to carry out saponification reaction;
4) adding water, cooling the system, and adding a reducing agent for reaction;
5) cooling the system, adjusting the pH value with acid, and performing post-treatment to obtain the delta caprolactone.
[2] The production process according to [1], wherein,
the beta-dicarbonyl compound in the step 1) is selected from one or more of acetylacetone, methyl acetoacetate, ethyl acetoacetate, octyl acetoacetate, oleyl acetoacetate, lauryl acetoacetate and stearyl acetoacetate.
[3] The production process according to [1] or [2], wherein,
the basic catalyst in the step 1) is selected from one or more of metal alkoxide, metal hydride, amidine, basic amine and metal phosphate.
[4] The production method according to any one of the aspects of [1] to [3], wherein,
the preheating in the step 1) refers to heating the system to 60-83 ℃.
[5] The production method according to any one of the aspects of [1] to [4], wherein,
the beta-dicarbonyl compound: alkyl acrylate: the molar ratio of the basic catalyst is 1.02-1.1: 1: 0.02-0.05.
[6] The production method according to any one of the aspects of [1] to [5], wherein,
the dropping speed of the acrylic acid alkyl ester in the step 2) is 25 g/min-65 g/min.
[7] The production method according to any one of the aspects of [1] to [6], wherein,
the temperature of the Michael addition reaction in the step 2) is 60-80 ℃.
[8] The production method according to any one of the aspects of [1] to [7], wherein,
the step of cooling the system refers to the step of cooling the temperature of the system to 5-0 ℃.
[9] The production method according to any one of the aspects of [1] to [8], wherein,
the reducing agent in the step 4) is selected from one or more of sodium borohydride, potassium borohydride and cyano sodium borohydride.
[10] The production method according to any one of the aspects of [1] to [9], wherein,
the post-treatment in the step 5) comprises extraction, desolventization and rectification.
ADVANTAGEOUS EFFECTS OF INVENTION
The preparation method of the invention obtains the product of delta caprolactone through Michael addition reaction, saponification reaction and reduction ring closure reaction. The synthetic method is novel, short in steps, high in raw material conversion rate, simple to operate, free of temperature explosion, relatively high in safety, greatly shortened in feeding time, short in total time consumption and free of carbon dioxide generation. In some embodiments of the invention, the conversion of the Michael addition reaction is greater than 94% (calculated on the equivalent of a slightly less alkyl acrylate) and the saponification and reduction reaction conversion is greater than 84% (calculated on the total moles of Michael addition product and Michael addition product produced by the Michael addition reaction), resulting in an overall process product yield of 78% or greater. Compared with the prior art, the method has the advantages of low requirement on equipment for reaction conditions, no potential safety hazard of high-pressure hydrogenation, capability of recycling the solvent and great reduction of comprehensive cost. The above description does not disclose all embodiments of the present invention and all advantages of the present invention.
Drawings
FIG. 1: chromatogram of the intermediate product of example 1 of the invention.
FIG. 2: nuclear magnetic spectrum of the product of inventive example 1.
FIG. 3: chromatogram of the intermediate product of example 2 of the invention.
Detailed Description
The following describes embodiments of the present invention, but the present invention is not limited to these embodiments. The present invention is not limited to the configurations described below, and various modifications are possible within the scope of the claims, and embodiments and examples obtained by appropriately combining the technical means disclosed in the respective embodiments and examples are also included in the technical scope of the present invention. All documents described in this specification are incorporated herein by reference.
Unless defined otherwise, technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.
The use of the terms "a" and "an" and "the" and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context.
In the present specification, a numerical range represented by "a value to B value" or "a value to B value" means a range including the end point value A, B.
In the present specification, the meaning of "may" includes both the meaning of performing a certain process and the meaning of not performing a certain process. In this specification, "optional" or "optionally" means that the subsequently described event or circumstance may or may not occur, and that the description includes instances where the event occurs and instances where it does not.
Reference throughout this specification to "some particular/preferred embodiments," "other particular/preferred embodiments," "some particular/preferred aspects," "other particular/preferred aspects," or the like, means that a particular element (e.g., feature, structure, property, and/or characteristic) described in connection with the embodiment is included in at least one embodiment described herein, and may or may not be present in other embodiments. In addition, it is to be understood that the described elements may be combined in any suitable manner in the various embodiments.
The term "comprises" and any variations thereof in the description and claims of the invention are intended to cover non-exclusive inclusions. For example, a process, method, or system, article, or apparatus that comprises a list of steps or elements is not limited to only those steps or elements listed, but may alternatively include other steps or elements not listed, or inherent to such process, method, article, or apparatus.
The invention provides a preparation method of delta caprolactone, which comprises the following steps:
1) dissolving a beta-dicarbonyl compound and a basic catalyst in a solvent for preheating;
2) dripping acrylic acid alkyl ester into the reaction system to carry out Michael addition reaction;
3) cooling the system, adding alkali, and then heating the reaction system to carry out saponification reaction;
4) adding water, cooling the system, and adding a reducing agent for reaction;
5) cooling the system, adjusting the pH value with acid, and performing post-treatment to obtain the delta caprolactone.
Wherein, step 1) and step 2) mainly relate to Michael addition reaction; step 3) involves a saponification reaction; the reduction reactions are mainly involved in step 4) and step 5).
Each reaction will be described below.
< Michael addition reaction >
The invention obtains a mixed intermediate by carrying out Michael addition reaction on a beta-dicarbonyl compound and alkyl acrylate under the action of a basic catalyst.
The β -dicarbonyl compound is a compound in which two carbonyl groups are separated by 1 saturated carbon atom in a molecule, and a methylene group between the two carbonyl groups in the β -dicarbonyl compound is changed into an active methylene group by the influence of the two carbonyl groups, and a hydrogen atom on the methylene group has a large acidity and is likely to form a carbanion under the action of a base, and thus, a Michael (Michael) addition reaction, which is a conjugate addition reaction of α, β -unsaturated aldehydes, ketones, carboxylic acids, esters, nitriles, nitro compounds, and the like, can be performed. In some embodiments of the invention, the beta-dicarbonyl compounds of the invention are preferably selected from beta-diketones and/or beta-ketoesters. Further, the beta-dicarbonyl compound of the present invention is selected from one or more of acetylacetone, methyl acetoacetate, ethyl acetoacetate, octyl acetoacetate, oleyl acetoacetate, lauryl acetoacetate, and stearyl acetoacetate. In view of raw material availability and cost, some embodiments of the invention the β -dicarbonyl compound is selected from the group consisting of acetylacetone, methyl acetoacetate. Further, for better control of the Michael addition reaction, acetylacetone is preferred, and this compound readily produces a monoaddition product.
The alkyl acrylate is an alkyl acrylate, and the alkyl group may be linear or branched. Examples of the alkyl acrylate include: methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, and n-octyl acrylate. In some embodiments of the invention, the alkyl acrylate is selected from methyl acrylate for reasons of raw material availability and cost.
The generation of carbanion from beta-dicarbonyl compound needs to be catalyzed by alkali, and the basic catalyst of the invention refers to a compound containing alkalinity capable of catalyzing the generation of carbanion from beta-dicarbonyl compound. In some embodiments of the invention, the basic catalyst used in the reaction is preferably selected from one or more of metal alkoxides, metal hydrides, amidines, basic amines. Specifically, the solvent may include one or more selected from sodium methoxide, sodium ethoxide, sodium tert-butoxide, potassium methoxide, potassium ethoxide, potassium tert-butoxide, 1, 8-diazabicycloundecen-7-ene (DBU), triethylamine and NaH. The basic catalyst of the present invention preferably does not include metallic sodium and metal hydroxide. Sodium metal is flammable and explosive and is not suitable for industrial production, and metal hydroxides such as sodium hydroxide generally cannot catalyze the reaction. The alkaline catalyst selected by the invention has better safety, is beneficial to industrial production and is beneficial to improving the yield of the reaction.
In consideration of the fact that sudden temperature jump occurs in the Michael addition reaction process and certain danger exists in the actual industrial production, few reports are made on the method for preparing the delta caprolactone. In order to further improve the safety, the beta-dicarbonyl compound and the basic catalyst are first dissolved in a solvent and preheated to prevent the temperature jump problem during the Michael addition reaction. In some embodiments of the invention, preheating refers to heating the system to a temperature of 60 ℃ to 83 ℃, further 60 ℃ to 80 ℃. If the temperature of preheating is too high, the problem of difficult control can occur when the boiling point of the solvent is exceeded; if the pre-heating temperature is too low, then a subsequent temperature burst may occur. The preheating temperature also affects the yield of the whole reaction, and in order to obtain a higher yield, the preheating temperature is more preferably from 65 ℃ to 75 ℃. The holding time or holding time after the preheating is not particularly limited, and may be usually 0.05 to 0.1 hour.
The kind of the solvent capable of dissolving the β -dicarbonyl compound and the basic catalyst is not particularly limited in the present invention, and any one or a mixed solvent of methanol, ethanol, acetonitrile, tetrahydrofuran, N-dimethylformamide, and N-methylpyrrolidone may be used. In some embodiments of the present invention, ethanol may be selected, and a condensing tube is usually added to the system during the preheating step, so that a small amount of volatile matter can be treated by the tail gas absorption system.
The alkyl acrylate is firstly added into a constant-pressure dropping funnel and then is dripped into a preheated reaction system, in some specific embodiments of the invention, the dripping time is 0.25-0.5 h, compared with the prior art, the dripping speed of the alkyl acrylate can be greatly improved because the preheating step is added, the dripping speed of the alkyl acrylate can be 25-65 g/min, further 40-60 g/min, and the dripping speed of the alkyl acrylate in the common patent document 1 is only 1.5 g/min. The present invention can significantly shorten the feeding time of the alkyl acrylate through the preheating step. And heating the reaction system to 60-80 ℃ after the alkyl acrylate is added, and carrying out Michael addition reaction, wherein in some specific embodiments of the invention, the temperature of the Michael addition reaction is 75-80 ℃ and is kept for 0.5-1 h.
In order to maximize the conversion, the amount of each raw material used in the reaction is, in some preferred embodiments of the present invention, slightly excessive β -dicarbonyl compound, and further, β -dicarbonyl compound: alkyl acrylate: the molar ratio of the basic catalyst is 1.02-1.1: 1: 0.02-0.05, and further the molar ratio of the basic catalyst to the basic catalyst is 1.03-1.1: 1: 0.03-0.05. The beta-dicarbonyl compound of the present invention and alkyl acrylate can be reacted almost completely using the above process and the amount of raw materials of the present invention, and the conversion of alkyl acrylate by Michael addition reaction is more than 94%.
The reaction product of this reaction is a mixed intermediate due to the presence of a basic catalyst. However, no additional work-up is required for this mixed intermediate and the next reaction step can be carried out directly to give the 5-oxohexanoate salt. For the case where the β -dicarbonyl compound is selected from acetylacetone and the alkyl acrylate is selected from methyl acrylate, the equation for the michael addition reaction is as follows:
< saponification reaction >
Considering that the addition of alkali is an exothermic reaction, in order to facilitate the subsequent addition and the temperature control of the system, the temperature of the system is required to be reduced after the Michael addition reaction is completed, and in some embodiments of the invention, the temperature can be reduced to 5 ℃ to 0 ℃. After the temperature is reduced, alkali is added, and then the reaction system is heated for saponification reaction.
The saponification reaction of the present invention refers to an ester hydrolysis reaction under base catalysis, and the purpose of the present invention is to convert all of the mixed intermediate of the Michael addition reaction into 5-oxohexanoate salts by hydrolysis. Compared with the scheme of preparing the acetylbutyric acid by adding the acid into the acetylsuccinate in the prior art, the method has the advantages of slow reaction, long time and easy incomplete reaction. In some preferred embodiments of the invention, the saponification reaction feedstock conversion is greater than 84%.
In some embodiments of the present invention, the base used in this step is a metal hydroxide, such as sodium hydroxide and/or potassium hydroxide, and specifically, a 20 to 40 wt% solution of sodium hydroxide or potassium hydroxide may be used. As for the amount of the base, the amount is preferably 2.0eq to 2.5eq from the viewpoint of conversion, and further 2.0eq to 2.1eq to more completely hydrolyze the ester group and acetyl group. After the addition of the base, in order to accelerate the reaction, the reaction system is preferably subjected to a temperature increase treatment, in some embodiments of the present invention, the temperature is increased to 60 ℃ to 70 ℃, and further, the reaction is continued at the temperature for 3h to 5 h.
The reaction is schematically represented by the following formula (taking sodium hydroxide as an example):
< reduction reaction >
After the saponification reaction is finished, water is added into the system, the system is cooled, and a reducing agent is added to carry out reduction ring-closing reaction.
In some embodiments of the invention, a small amount of water is added to the system after the saponification reaction is complete to dilute the system. In some embodiments of the invention, a small amount of water is typically equivalent to twice the weight of the starting alkyl acrylate.
In order to facilitate the subsequent feeding and reaction temperature control, the system needs to be cooled after a small amount of water is added. In some embodiments of the invention, the temperature may be reduced to 5 ℃ to 0 ℃.
Then adding a proper amount of reducing agent to react. In some embodiments of the present invention, the reducing agent is selected from one or more of sodium borohydride, potassium borohydride, and sodium cyanoborohydride. Compared with the hydrogenation reduction method in the prior art, the reduction method adopted by the invention does not need to use a noble metal catalyst, does not use high-pressure reaction conditions, and has the advantages of lower cost, easier control of reaction and higher safety. The amount of the reducing agent is preferably 1.0eq to 1.5eq, and more preferably 1.0eq to 1.2eq, from the viewpoint of conversion. In some preferred embodiments of the invention, the reduction reaction feedstock conversion is greater than 84%.
The schematic reaction of this reaction is as follows:
and after the reduction reaction is finished, cooling the system, adjusting the pH value with acid, and performing post-treatment to obtain the delta caprolactone. In some embodiments of the invention, the temperature may be reduced to 5 ℃ to 0 ℃. The pH is adjusted with an acid, and the kind of the acid used is not particularly limited in the present invention, and examples thereof include inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid. The amount of the acid used is usually 2.05eq to 2.3eq, and more usually 2.1eq to 2.2 eq. The pH value of the system is adjusted to 1-2, preferably 1 by adding acid, and the system is stirred for 1-3 h, wherein the acidic condition is favorable for the reduced 5-hydroxy methyl caproate to smoothly close the ring by itself.
In some embodiments of the invention, the aforementioned post-treatments of the invention include extraction, desolventization and rectification. Further, adding organic solvent such as dichloromethane for extraction, vacuum desolventizing, and rectifying to obtain the product of the caprolactone.
The whole process is simple to operate, and the product yield of the whole process reaches over 78 percent. Compared with the prior art, the method has the advantages of low requirements on equipment for reaction conditions, no potential safety hazard of high-pressure hydrogenation, no potential safety hazard of temperature explosion, high raw material utilization rate, no carbon dioxide emission, capability of recycling the solvent and greatly reduced comprehensive cost.
The invention is further illustrated, but not limited, by the following examples.
Examples
Example 1
Acetylacetone (1050 g, 10.5mol) and sodium methoxide (16.2 g, 0.3mol) were dissolved in ethanol (1000 g), and the reaction system was heated to 68 ℃ for 5 minutes. Methyl acrylate (860 g, 10mol) was added dropwise to the above system using a constant pressure dropping funnel over a period of 0.25h, and after the end of the addition, the reaction system was heated to 80 ℃ and held for 0.5 h. After the reaction is finished, the intermediate product is analyzed by a WH-500 chromatographic analyzer, and the result is shown in FIG. 1, wherein in FIG. 1, the peak value 1.59 is a solvent ethanol peak, the peak value 4.85 is methyl 5-oxohexanoate, the peak value 8.37 is methyl 4-acetyl-5-oxohexanoate, and the sum of the integral areas of the two peak values is more than 95%, thereby showing that the conversion rate of the Michael addition reaction alkyl acrylate is more than 95%.
The temperature was then reduced to 0 ℃ and 30% sodium hydroxide solution (2670 g, 20mol) was added. The temperature of the reaction solution is raised to 65 ℃, and the reaction is continued for 4 hours. After the reaction, a small amount of water was added, the temperature was reduced to 0 ℃ and sodium borohydride (399 g, 10.5mol) was added to carry out the reaction. After the reaction is finished, the temperature is reduced to 0 ℃, the pH value is adjusted to 1 by hydrochloric acid (30 percent, 3000 g, 2.4mol), and the mixture is stirred for 1 to 3 hours. Extraction was performed by adding methylene chloride (1000 ml), methylene chloride was removed, and the concentrate was rectified to give delta caprolactone (891 g, yield 78%, purity 98.1%). The result of the nuclear magnetic assay of the product is shown in FIG. 2, and it is understood from FIG. 2 that caprolactone was indeed synthesized.
Example 2
Acetylacetone (1050 g, 10.5mol) and sodium methoxide (16.2 g, 0.3mol) were dissolved in ethanol (1000 g), and the reaction system was heated to 83 ℃ under strong reflux for 5 minutes. Methyl acrylate (860 g, 10mol) was added dropwise to the above system using a constant pressure dropping funnel over a period of 0.25h, and after the addition was completed, a temperature controller was heated to maintain the reaction system at 80 ℃ for 0.5 h. After the reaction is finished, the intermediate product is analyzed by a WH-500 chromatographic analyzer, and the result is shown in FIG. 3, wherein in FIG. 3, the peak value 1.61 is a solvent ethanol peak, the peak value 4.89 is methyl 5-oxohexanoate, the peak value 8.65 is methyl 4-acetyl-5-oxohexanoate, and the sum of the integrated areas of the two peak values is more than 94%, thereby indicating that the conversion rate of the Michael addition reaction alkyl acrylate is more than 94%.
The temperature was then reduced to 0 ℃ and 30% sodium hydroxide solution (2670 g, 20mol) was added. The temperature of the reaction solution is raised to 65 ℃, and the reaction is continued for 4 hours. After the reaction, a small amount of water was added, the temperature was reduced to 0 ℃ and sodium borohydride (399 g, 10.5mol) was added to carry out the reaction. After the reaction is finished, the temperature is reduced to 0 ℃, the pH value is adjusted to 1 by hydrochloric acid (30 percent, 3000 g, 2.4mol), and the mixture is stirred for 1 to 3 hours. Adding dichloromethane (1000 ml) for extraction, removing dichloromethane, and rectifying the concentrate to obtain delta caprolactone (861 g, yield 75.5%, purity 98.03%)
Comparative example 1
Anhydrous ethanol (4L) was added to the reaction flask and fragmented sodium (4.4 g, 0.19mol) was slowly added to the ethanol at room temperature (about 20 ℃). And cooling the system to 0 ℃ after the system is completely dissolved. Acetylacetone (1000 g, 10mol) was added dropwise at 0 ℃ over 20 minutes, and then methyl acrylate (860 g, 10mol) was added dropwise at 0 ℃ over 20 minutes, and heating of the reaction system was started after the end of the addition. Heating to the internal temperature of about 70 ℃, suddenly starting the reaction to be violent, stopping heating, continuously raising the internal temperature of the reaction system to 95-96 ℃, violently refluxing for 44 minutes, slowly refluxing by virtue of a violent reflux flow, controlling the external temperature by virtue of a temperature controller, and continuously keeping the external temperature in a refluxing state for 20 minutes at 85 +/-2 ℃. After the reaction was complete, the temperature was reduced to 0 ℃ and 30% sodium hydroxide solution (2670 g, 20mol) was added. The temperature of the reaction solution is raised to 65 ℃, and the reaction is continued for 4 hours. After the reaction, a small amount of water was added, the temperature was reduced to 0 ℃ and sodium borohydride (399 g, 10.5mol) was added to carry out the reaction. After the reaction is finished, the temperature is reduced to 0 ℃, the pH value is adjusted to 1 by hydrochloric acid (30 percent, 3000 g, 2.4mol), and the mixture is stirred for 1 to 3 hours. Extraction was performed by adding methylene chloride (1000 ml), methylene chloride was removed, and the concentrate was rectified to give delta caprolactone (731 g, 64% yield, 98.0% purity).
Comparative example 2
Anhydrous ethanol (1L) was added to the reaction flask and fragmented sodium (4.4 g, 0.19mol) was slowly added to the ethanol at room temperature (about 20 ℃). And cooling the system to 0 ℃ after the system is completely dissolved and cleared. Acetylacetone (1000 g, 10mol) was added dropwise at 0 ℃ for 20 minutes, and then methyl acrylate (860 g, 10mol) was added dropwise at 0 ℃ for 20 minutes, and heating of the reaction system was started after the end of the addition. When the temperature is heated to about 68 ℃ of the internal temperature, the reaction suddenly starts to be violent, the heating is stopped, the internal temperature of the reaction system continuously rises and the reaction system vigorously refluxes, after about 2 minutes, the ethanol is not condensed and vigorously overflows, the internal temperature is higher than 187 ℃, the ethanol is rapidly dispersed into a large amount of ice blocks, and the reaction is ended and cannot be continued.
Comparative example 3
Sodium hydroxide (9 g, 0.225mol) and ethyl acetoacetate (1040 g, 8mol) are added into a reactor provided with a stirrer, a thermometer and a dropping funnel, the rotating speed is controlled to be 135 r/min, the temperature is controlled to be 30 ℃, stirring is carried out, the mixture is dropwise added (344 g, 4mol), the dropwise adding time is 4 hours, after the dropwise adding is finished, stirring is continued for 4 hours, the main peaks are still raw materials of ethyl acetoacetate and methyl acrylate detected by gas chromatography, and the content of two other small impurities is less than 10 percent, and the reaction is judged to be almost impossible.
As can be seen from the comparison of examples and comparative examples, if the preheating step is not used, the Michael addition reaction is liable to suffer from a temperature jump, and in a serious case, the reaction cannot be continued. The whole process of the scheme of the invention has simple operation, short whole time consumption, high product yield of over 78 percent, low requirement on equipment and better safety.
The above examples are intended only to illustrate several embodiments of the present invention, which are described in more detail and detail, but are not to be construed as imposing any limitation on the scope of the present invention. It should be clear that a person skilled in the art can make several variations and modifications without departing from the inventive concept, which fall within the scope of protection of the present invention.
Claims (10)
1. A method for preparing delta caprolactone, which is characterized by comprising the following steps:
1) dissolving a beta-dicarbonyl compound and a basic catalyst in a solvent for preheating;
2) dripping acrylic acid alkyl ester into the reaction system to carry out Michael addition reaction;
3) cooling the system, adding alkali, and then heating the reaction system to carry out saponification reaction;
4) adding water, cooling the system, and adding a reducing agent for reaction;
5) cooling the system, adjusting the pH value with acid, and performing post-treatment to obtain the delta caprolactone.
2. The production method according to claim 1,
the beta-dicarbonyl compound in the step 1) is selected from one or more of acetylacetone, methyl acetoacetate, ethyl acetoacetate, octyl acetoacetate, oleyl acetoacetate, lauryl acetoacetate and stearyl acetoacetate.
3. The production method according to claim 1 or 2,
the basic catalyst in the step 1) is selected from one or more of metal alkoxide, metal hydride, amidine, basic amine and metal phosphate.
4. The production method according to any one of claims 1 to 3,
the preheating in the step 1) refers to heating the system to 60-83 ℃.
5. The production method according to any one of claims 1 to 4,
the beta-dicarbonyl compound: alkyl acrylate: the molar ratio of the basic catalyst is 1.02-1.1: 1: 0.02-0.05.
6. The production method according to any one of claims 1 to 5,
the dropping speed of the acrylic acid alkyl ester in the step 2) is 25 g/min-65 g/min.
7. The production method according to any one of claims 1 to 6,
the temperature of the Michael addition reaction in the step 2) is 60-80 ℃.
8. The production method according to any one of claims 1 to 7,
the step of cooling the system refers to the step of cooling the temperature of the system to 5-0 ℃.
9. The production method according to any one of claims 1 to 8,
the reducing agent in the step 4) is selected from one or more of sodium borohydride, potassium borohydride and cyano sodium borohydride.
10. The production method according to any one of claims 1 to 9,
the post-treatment in the step 5) comprises extraction, desolventization and rectification.
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| CN112028755A (en) * | 2020-09-24 | 2020-12-04 | 青岛科技大学 | Method for preparing 1,3 cyclohexanedione |
| CN112321552A (en) * | 2020-11-10 | 2021-02-05 | 安徽华业香料合肥有限公司 | Synthesis method of delta-caprolactone spice |
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| CN112028755A (en) * | 2020-09-24 | 2020-12-04 | 青岛科技大学 | Method for preparing 1,3 cyclohexanedione |
| CN112321552A (en) * | 2020-11-10 | 2021-02-05 | 安徽华业香料合肥有限公司 | Synthesis method of delta-caprolactone spice |
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| CN114516796A (en) * | 2022-03-30 | 2022-05-20 | 北京化工大学 | Method for preparing 5-oxohexanoate |
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